The present invention relates to an evaporation chamber for use with portable engines for gas-powered tools such as hand-held fastening or cutting tools.
In order to accurately measure and inject small amounts of fuel into a combustion chamber such as can be used in gas-powered fastening tools, it is desirable to convert a liquefied petroleum gas, such as propane or Mapp gas, from a removable container into its vapor state. The fuel can be more easily measured as a gas than as a liquid.
Attempts such as those that appear in U.S. Pat. Nos. 6,016,946 and 6,045,024, which utilize a two-stage regulator, and another that appears in U.S. Pat. No. 5,873,508, which utilizes a single-stage regulator, have poor performance characteristics during periods of high cycling rates or low ambient temperature whereby liquid fuel can get past the regulators. Excess fuel reaching the fuel injector can cause the tool to misfire.
Thus, it is an object of this invention to correct the aforementioned problem under all normal operating conditions. Another object is to provide a durable, inexpensive, and replaceable valving and sealing system in a simple package.
In accordance with one or more embodiments of the present invention, an evaporation chamber system is provided for use with engines for gas-powered tools to convert liquefied petroleum (LPG) to its vapor state. An exemplary system has an evaporation chamber with an intake check valve at an inlet end to communicate with a source of LPG. The system also has a regulator valve situated at a location remote from the intake check valve through which fuel from the evaporation chamber is passed towards a combustion chamber of the engine. The intake check valve is arranged to deliver a charge of LPG to the evaporation chamber for evaporation into a gaseous state at a lower pressure than that existing at the source of LPG. The regulator valve is arranged to deliver the charge or a portion of it in the gaseous state to the combustion chamber for combustion (for example, by way of a portioning or metering valve).
In a preferred embodiment of the present invention, the regulator valve has an inlet port positioned and extending into a central region of the evaporation chamber so as to permit the inlet port to be located above any liquid level normally found in the evaporation chamber, regardless of the orientation of the evaporation chamber system.
The invention can also be practiced as a method of converting a liquefied fuel to its vapor state for supplying the fuel to a gas-powered engine. The method includes supplying a liquefied fuel from a pressurized source and conveying the liquefied fuel from the pressurized source to an evaporation chamber through a first pressure reducer (e.g., the intake check valve). The liquefied fuel is converted from a liquid state to a gaseous state within the evaporation chamber at a pressure substantially above ambient atmospheric pressure. The gaseous-state fuel from the evaporation chamber is conveyed towards a combustion chamber of the engine through a second pressure reducer (e.g., the regulating valve).
Preferably, the step of conveying the gaseous-state fuel from the evaporation chamber includes conveying the fuel to a portion system at a preset pressure that is less than the pressure in the evaporation chamber and is more than the ambient atmospheric pressure. The gaseous-state fuel is further preferably conveyed from the evaporation chamber through a port located above any liquid fuel levels normally found in the evaporation chamber throughout a range of angular orientations of the evaporation chamber.
Benefits can also be obtained by positioning the evaporation chamber in thermal communication with the gas-powered engine and removably mounting the intake valve within the evaporation chamber.